This invention relates to chain saws, and especially to a safety device for preventing the cutter chain from moving when the user grips the saw mechanism with only one hand.
Conventional chain saws have a trigger mechanism built into a longitudinally extending hand grip device located above the engine housing The trigger mechanism is linked to a carburetor throttle operator arm, such that a manual squeeze force on the trigger mechanism can cause the engine to develop full power, for thereby moving the cutter chain at relatively high cutting speeds. It is thus possible for the outdoorsman to operate a chain saw with only one hand.
However, one handed operation of a chain saw can be dangerous to the user. He may not have firm control of the saw, and he runs the risk of cutting himself with the moving cutter chain. For example, he may hold a tree branch with one hand while attempting to manipulate the chain saw with his other hand, running the risk of cutting his hand or arm along with the tree branch.
One handed operation of a chain saw may also be dangerous at start-up. Often the outdoorsman will hold the saw mechanism in one hand while pulling the starter cord with his other hand. The reaction forces can cause the cutter chain to swing downward so as to cut into the user's foot or leg.
The present invention contemplates a safety device that is attachable to a conventional chain saw to require the user to have two hands on the saw mechanism before it is possible for the cutter chain to move. The safety device is preferably constructed as an attachment for existing chain saws.